In conventional internal combustion engines for automobile use, an electromagnetic fuel injection valve driven by the electrical signals sent from the engine control unit is commonly used.
This type of fuel injection valve is constructed so that: an electromagnetic coil and a yoke are arranged around a hollow tubular type of fixed core (center core); a nozzle body containing a needle equipped with a valve body is installed at the bottom of the yoke which accommodates the electromagnetic coil, and; the needle is energized towards the valve seat by the action of the return spring.
Proposed an example of such a conventional electromagnetic fuel injection valve is, as disclosed in, for example, Japanese application patent laid-open publication No. Hei-10-339240 or Hei-11-132127, a single one into which a magnetic fuel connector portion, a non-magnetic intermediate pipe portion, and a magnetic valve body portion were molded by magnetizing one pipe formed of a composite magnetic material and then non-magnetizing only the intermediate portion of this pipe by use of, for example, induction heating, in order to reduce the number of parts and facilitate the assembly of the parts.
For this type, a cylindrical fixed core is press-fit in a fuel connector portion and a movable core with a valve body is mounted in the valve body portion. Also, an electromagnetic coil is provided on the intermediate periphery of the pipe and a yoke is provided outside the electromagnetic coil. When power is supplied to the electromagnetic coil, a magnetic circuit is formed over the area from the yoke to the fuel connector portion, the fixed core, the movable core, the valve body portion, and the yoke, and the movable core is magnetically attracted towards the fixed core. The non-magnetic portion functions as a magnetic flux short-circuiting suppressor between the fuel connector portion and the valve body portion.